1. Field of the Invention
The present invention relates to an electric connecting apparatus for semiconductor devices configured to electrically connect semiconductor devices as a first contacted object, such as semiconductor wafer, bear chip, integrated circuit package, and liquid crystal display panel, with a wiring substrate as a second contacted object in order to conduct an inspection electrically, and a contact used therefor.
2. Description of the Related Art
In a process of manufacturing semiconductor devices such as semiconductor wafers, bear chips, integrated circuit packages (also referred to as “IC package”), and liquid crystal display panels (also referred to as “LCD panels”), various tests are conducted for inspecting the presence or absence of defectives in the semiconductor devices. As one of these tests, an inspection conducted by applying a test signal to the semiconductor devices as inspected objects and inspecting electric characteristics of the semiconductor devices is known. In general, such kind of test is conducted via an electric connecting apparatus (hereinafter, referred to simply as “IC socket”) for semiconductor devices configured to electrically connect the inspected object and a wiring substrate such as a test board. As the IC socket as described above, an IC socket which is disclosed in Japanese Patent Laid-Open No. 2004-152495 is known.
In the IC socket which is disclosed in Japanese Patent Laid-Open No. 2004-152495, a contact including a plunger formed by punching a metal sheet into a predetermined shape via a press work and a coil spring resiliently urging the plunger is used. The plunger is placed in an though hole having a small-diameter portion and a large-diameter portion and being formed on an insulating base plate which constitutes a socket base of the IC socket so as to be able to move upward and downward therein. The plunger includes a terminal portion coming into contact with an external contact point of the semiconductor device (normally, formed as a solder ball) and is placed in the through hole in such a manner that the distal end of the terminal portion of the plunger projects upward from the through hole.
As disclosed in Japanese Patent Laid-Open No. 2004-152495, the plunger which constitutes the contact is formed simply by punching the sheet metal into the predetermined shape via the press work. Therefore, the plunger is shaped into a flat sheet, and does not have a structure to control transfer in the direction of thickness thereof. The terminal portion of the plunger which comes into contact with the semiconductor device as a contacted object is formed to come into contact with a corresponding external contact point of the semiconductor device at two points.
The plunger which constitutes the contact is configured as described above, is easily inclined with respect to the through hole formed on the insulating base plate which constitutes the IC socket, so that the positional accuracy of the terminal portion of the plunger is not stabilized. In other words, when the semiconductor device mounted on the IC socket and the contact come into contact with each other, the plunger of the contact is pressed in an inclined state, and the coil spring which supports the plunger is compressed. In this case, the contact position between the terminal portion of the plunger and the external contact point of the semiconductor device may be unstable due to the inclination of the plunger. Therefore, when the contact at a predetermined contact position is not achieved, a predetermined contact pressure might not be obtained between the terminal portion and the external contact point due to an insufficient amount of displacement of the contact. Accordingly, the result of inspection relating to the electric characteristics of the IC package, which should be essentially determined to be normal, might become “defective”, so that the yield of the IC packages may be lowered.
Also, when the semiconductor device as the contacted object is an IC package of BGA (Ball Grid Array), the plunger is inclined with respect to the through hole, whereby an event such that the terminal portion of the plunger comes into contact with a side surface of a ball-shaped terminal (also referred to as “solder ball”) as an external contact point of the IC package may occur. There is also a risk of formation of a contact mark on the side surface of the solder ball by the plunger due to the side surface contact of the plunger with respect to the solder ball. By the formation of the contact mark on the side surface of the solder ball by the plunger, the IC package, which should be essentially determined to be normal in an appearance inspection of the semiconductor device, is determined to be defective, so that the yield of the IC packages is lowered in this case as well.
Furthermore, when the solder balls of the IC package get the contact marks on a position which is not the predetermined position, specifically on top surfaces thereof, the respective solder balls may have different heights. Consequently, when mounting the IC package on an electronic apparatus, it might not be mounted correctly.
It is contemplated to prevent the inclination of the plunger by forming the through hole on the insulating base plate into a square shape in cross section, as disclosed in Japanese Patent Laid-Open No. 2004-152495. However, in recent years, the pitches between the plurality of external contact points formed on the semiconductor devices such as the IC packages tend to be finer, and hence it is very difficult to form the square-shaped through holes.